In one approach charge balancing circuits (passive) discharge one or more cells of a battery to bring all of the cells into balance to improve battery life. Typically this is done by controlling the leakage current from each cell individually. For example, a transistor switch and series resistance are configured in parallel with each cell. The switch is turned on for a predetermined time depending on the over charge of the associated cell, e.g. the greater the over charge the longer the switch is held on to continue the discharge. One shortcoming with this is that, in a multicell battery where only one or a few cells are under charged, it is inefficient to discharge the majority of cells to bring them down to the charge level of the few undercharged. Another approach (active) is to apply a charge, e.g. via a flying capacitor to the one or few cells that are under charged to bring them up to the charge levels of the others. This requires a complex matrix of switches to selectively apply the charge to the cells which are under charged.